Small threading tool insert tool review

[marfaguy]

 A friend of mine’s girl friend is really into Science fiction / Fantasy, especially the Hellboy franchise. 

She has a “Samaritan” replica revolver in caliber “ Break your wrist even if you’re Arnold S.” 
http://www.mwctoys.com/REVIEW_111008a.htm 
but the “ammo” is not very well made, in fact two of the plastic rounds had separated at the base. 
So my friend asked me if I could remake a couple of them with real brass casings, thread the internal parts, etc. 
The originals are plastic with a base insert. The base is a semi tight insert with a “firing pin”
that actuates a flashing LED. The bullet is clear plastic, probably an acrylic of some sort, that magnifies the flashing LED. 

 Anyway I wanted to thread the base to the casing with some fine threading. I’ve had so-so results
with internal threading with my home made threading tools so I decided to try a commercial threading 
insert tool and holder. I’ve had good experiences with Shars both in terms of price and quality so after 
some research I ordered the Internal Threading Toolholder 3/8" Shank for 1/4" Insert.
http://www.shars.com/products/view/7807/Internal_Threading_Toolholder_38quot_Shank_for_14quot_Insert

 I’m planning on doing the final rounds in brass and given the sizes (.600” internal and a bit over .8 O.D”) I decided to try it first in some aluminum.
I drilled out then bored some ally to .600 +-.0002 and left the O.D. at 1” accept for a skim to make it concentric. 
I then loaded up the tool and set my lathe for 32 T.P.I. 

 As can be seen from the catalog link http://www.shars.com/files/products/cata...page79.pdf
the toolholder holds the insert at a downward angle providing, if I have terminology correct, rake. 
In other words the cutting point itself is somewhat pointing downward when mounted upright in a tool holder. 

 After confirming my T.P.I. I made the first cut pass at .010” with the provided PC TIN coated insert. The chip came off clean
and full length ( about 5/16” total length). A second spring cut pass produced a very small whisker of a cut. A third pass produced nothing. 

 I had very similar results with subsequent cuts all the way to .028” where I made 2 spring cuts just to make sure the threading was fully clear. 
I was impressed with quality of the cut, even though this was just in aluminum. 

 After parting off the body of the casing I turned my attention to the base. Since the focus of this post is on the internal 
threading tool I’ll dispense with a description of setting up and executing the external threading. Suffice to say it went normally. 

 So how did the tool work? Really well I think. While examining the cut there was obviously less tear out then with my other internal threading tools.
Spring cuts produced less chip at least implying better initial cutting action. The fit of mating parts feels very smooth with very little to no slop. 

I Like it and would recommend it. Especially if you work mostly in soft metals like ally or brass/bronze. I don’t know how long the supplied insert
would last with softer metals but I wouldn’t be surprised if it’s months or a lifetime depending on usage. 

[PixMan]

I have the similar tool from Carmex, though arguably better quality being made in Israel rather than China. The two biggest makers of carbide insert threading tools are Vargus/Vardex and Carnex, both based there. Most of the major brands such as Kennametal, Iscar, Walter-Valenite, Seco and others get their tools from one of those two companies and rebrand it.

You would get the most out of the tool by buying the pitch-specific "cresting" (a.k.a. full form) threading inserts. With the similar external tools (which generally use the larger 3/8" I.C. size inserts, you get the same kind of results with an even better characteristic. You leave the O.D. at nominal and when your threading insert takes the O.D. down to spec, the pitch diameter is DONE.